Order of keys

[Steve Matzura]

I hope I'm asking this on the right list, in the right place. I go
through this every three years and for whatever reason keep forgetting
to record how this works!

In the Dovecot config, there are two places to define SSL
certificates--ssl_cert_file and ssl_key_file. My question is this:
Which two of the three files--the certifying authority, the signed
certificate for the specific system, and the private certificate
file--are combined to create the file that goes with ssl_cert_file?
Since there are six possible permutations to answer this question
(because order of files matters), which two go with ssl_crt_file and
in what order? I have a private certificate file, the certifying
authority's .CRT file, and the certifying authority's signed .PEM file
which contains the system's certified certificate.

Thanks in advance.